In Japanese Patent No. 3652487, an identification medium having a cholesteric liquid crystal layer subjected to hologram processing is described. In Japanese Unexamined Patent Application Publication No. 2007-1130, an identification medium is described in which a phase difference layer is stacked on a reflection layer, a phase difference is changed at a portion thereof by heating, and a latent image is thereby observed via a polarization filter. In Japanese Unexamined Patent Application Publication No. 2009-175208, an identification medium is described in which an area in which a phase difference is different is provided, and a latent image having a different color is thereby observed via a polarization filter.
In the technique disclosed in Japanese Patent No. 3652487, an image having a specific color can be used for identification. However, when a light reflected from one cholesteric liquid crystal layer is used, an image having plural colors (for example, an image having green and red) cannot be used for identification. In the techniques disclosed in Japanese Unexamined Patent Application Publications Nos. 2007-1130 and 2009-175208, when the polarization filter is spaced away from the identification medium, lights having various phase conditions enter the identification medium. Thus, selectivity of reflection wavelength due to the phase difference layer (that is, characteristics that light of specific wavelength selectively passes through the phase difference layer) and specific polarized characteristics of light passing therethrough may be weak, so that the observed image and the color thereof may be unclear. Due to this, in order to obtain identification function from the identification medium, it is necessary that the polarization filter be contacted to or be disposed close to the identification medium. As a result, use of the identification medium may be limited.